Repair manual

SULEV 2.0L TFSI Engine
40
Catalyst Heating with Dual Injection
and Secondary Air Injection
To achieve good idling quality, a special characteristic
map has been selected. In this map the following
parameters relevant to exhaust emissions have been
adapted:
– Fuel rail pressure
– Injection timing of first injection during the intake
phase
– Injection timing of second injection during the
compression phase
– Fuel split during first and second injections
(approximately 70% during first injection)
– Intake camshaft adjustment
– Position of the intake manifold flaps (open/closed)
– Ignition angle adjustment towards retard (up to 21°
after TDC)
– Combustion chamber air ratio
By using the secondary air system, exhaust gas
temperature has been increased while reducing
hydrocarbon emissions.
Dual Injection During the Engine
Warm-Up Phase
The catalytic converter heat-up phase is followed by
the engine warm-up phase, where one dual injection is
performed per working cycle. The main part of the fuel
charge (approximately 80%) is injected synchronous with
the intake cycle, and the remainder (approximately 20%)
during the compression phase.
During the engine warm-up phase, dual injection is
performed within the mapped range at engine speeds of
less than 3000 rpm. At the same time, the intake manifold
flaps are closed to increase flow intensity.
The advantage of this operating mode is that
considerably less fuel is deposited on the cylinder walls
due to the low penetration depth of the fuel during
second injection when the engine is still not fully warmed
up.
Raw hydrocarbon emissions are lower, and entrainment
of fuel into the engine oil is kept to a minimum.
Crankshaft Angle [°]
1
2
3
Charge Cycle TDC
BDC
Ignition TDC
Fuel Quantity [%]